Brazilian Santa Inês (SI) sheep are very well-adapted to the tropical conditions of Brazil and are an important source of animal protein. A high rate of twin births was reported in some SI flocks. Growth and Differentiation Factor 9 (GDF9) and Bone Morphogenetic Protein 15 (BMP15) are the first two genes expressed by the oocyte to be associated with an increased ovulation rate in sheep. All GDF9 and BMP15 variants characterized, until now, present the same phenotype: the heterozygote ewes have an increased ovulation rate and the mutated homozygotes are sterile. In this study, we have found a new allele of GDF9, named FecG(E) (Embrapa), which leads to a substitution of a phenylalanine with a cysteine in a conservative position of the mature peptide. Homozygote ewes presenting the FecG(E) allele have shown an increase in their ovulation rate (82%) and prolificacy (58%). This new phenotype can be very useful in better understanding the genetic control of follicular development; the mechanisms involved in the control of ovulation rate in mammals; and for the improvement of sheep production.

Superovulation in ewes has been a source of many studies aimed at obtaining high superovulatory response and number of viable embryos recovered. In a protocol called Day 0, superovulatory treatment was initiated at the time of wave emergence in the absence of a dominant follicle (Menchaca A et al. 2002 Theriogenology 58, 1713-1721). The aim of this study was to compare ovarian response and number of embryos recovered after treatment between ewes treated with a Day 0 protocol and those treated with a traditional protocol. Santa InÊs ewes (n= 18) between 2 and 5 years old were randomly distributed into 2 superovulation treatment groups: traditional protocol and Day 0 protocol. Each treatment was repeated twice in a crossover model. The traditional protocol consisted of the intravaginal insertion of a sponge containing 60 mg of medroxiprogesterone acetate (MAP; Progespon®, Tecnopec, São Paulo, Brazil) for 14 days, which was replaced on Day 7, followed by 150 μg of cloprostenol (Prolise®, Tecnopec) i.m. On Day 12, FSH (Folltropin®-V, Bioniche, Belleville, Ontario, Canada) treatment was initiated using a total dose of 200 mg, given in twice-daily i.m. injections that decreased in dose over 4 days. A dose of 200 IU of eCG (Novormon®, Syntex, Buenos Aires, Argentina) i.m. was given at the time of sponge withdrawal. The AI was done by laparoscopy at 48 and 55 h after sponge withdrawal using fresh semen. The Day 0 protocol consisted of a previous 9-day synchronization treatment with a sponge containing 60 mg of MAP, followed by 150 μ of cloprostenol i.m. and 200 IU of eCG i.m. given on Day 7. A dose of 0.05 mg of GnRH (lecirelin; Gestran Plus®, Tecnopec) i.m. was given 16 h after sponge withdrawal. In a preliminary study, 38 ewes ovulated 42 ± 52 h after sponge withdrawal. Therefore, 48 h after sponge removal was considered as Day 0 and FSH treatment was initiated at that time, with a total dose of 200 mg of Folltropin®-V, given in 6 twice-daily decreasing doses. Two doses of cloprostenol (150 μg) were given i.m. concurrent with the fifth and sixth FSH treatments. Gonadotropin-releasing hormone (0.05 mg of lecirelin i.m.) was given 12 h after the last FSH treatment. Artificial insemination with fresh semen was done by laparoscopy 16 and 26 h after GnRH treatment. Five days after AI, embryos were recovered surgically. Results were evaluated by the parametric t-test. The number of corpora lutea and ova/embryos recovered did not differ (P > 0.05) between the traditional (9.8 ± 5.3; 4.5 ± 4.6) and Day 0 (10.0 ± 6.0; 3.5 ± 4.3) protocols. Similarly, no difference in the number of viable embryos was observed between treatments (1.6 ± 2.0 and 1.7 ± 2.4 for the traditional and Day 0 treatments, respectively). Within viable embryos, the traditional protocol (0.4 ± 1.0) resulted in ahigher (P < 0.05) number of morulae than that of the Day 0 protocol (0.1 ± 0.3). The ewes that had no superovulatory response did not differ (P > 0.05) between the traditional (11.11%) and Day 0 (5.56%) protocols. In summary, there was no difference in the parameters evaluated between both protocols. Financial support: FAPDF, CNPq, Tecnopec.